Pendulum rolling resistant test

ABSTRACT

A pendulum device is used to test the rolling resistance of a material. The device includes a rolling unit for contact with the material being tested, an assembly for initiating pendulum motion of the device, and measuring the amplitude of the pendulum motion over time. The rate of decrease of the amplitude of the pendulum motion is a measure of the rolling resistance of the material.

TECHNICAL FIELD

The invention relates to apparatus for testing the rolling resistance ofmaterials.

BACKGROUND

For product comparison between competitors, and for researching ways toimprove elastomeric products, a means is needed for measuring therolling resistance of products such as conveyor belts, and elastomericcomponents such as plies or tread used in pneumatic tires. In the priorart, most apparatus and methods for measuring rolling resistance aredirected at measuring components of rolling resistance such ashysteresis, G', modulus and the like. Using these parameters, anapproximation of rolling resistance can be obtained.

The advantage of approximating rolling resistance based on relatedparameters is that only very small amounts of material are needed tomeasure the related parameters. The disadvantage is that the measuredparameters do not always interact the same way in different materials toprovide an accurate estimation of rolling resistance, and there is noway to predict the contribution of the various parameters in a specificproduct construction, and the approximations are sometimes incorrect bya substantial margin.

Accordingly, it is an object of the present invention to provide amethod and apparatus for directly measuring the rolling resistance of amaterial, especially an elastomeric material, using a relatively smallsample of the material.

1. Background Art

At the annual meeting of the Adhesion Society, held, in Savannah, Ga.,Feb. 22-25, 1998, Professor M Chaudhury of Leheigh University presenteda poster describing research in which an oscillating rubber roller wasused to study adhesion on flat surfaces, using the energy expended asthe roller rocked backwards and forwards on a chemically-modified flatsurface to measure the difference between energy loss in breakingcontact and energy gained on making contact.

Rubber covered rollers have been described by M Hannah,Quart.J.Mech.Appl.Math., 4, 95-105 (1951); G. J. Parish,Brit.J.Appl.Phys., 9, 158-161 (1958); G. J. Parish, Brit.J.Appl.Phys.,9, 428-433 (1958); G. J. Parish, Brit.J.Appl.Phys.12,333-335 (1961); M.Barquins and Efelder, Kautschuk u. Gummi 43,no.2, 114-117(1990); F.Zeppernick, Gummi Fasern Kunststoffs 44, 654(1991) to 46,580(1993).

2. Disclosure of Invention

An apparatus for measuring the rolling resistance of a substratecomprises a rolling means for rolling contact with a surface to bemeasured, an arm attached to the rolling means and extending downwardfrom said rolling means to free space below the rolling means, a swingweight integral with or attached to the arm distal from the rollingmeans and in the free space, and measuring means located near the freespace for measuring the location of the swing weight relative to themeasuring means.

The apparatus may further comprise a lever attached to the rolling meansfor controlling the initial amplitude of the swing weight when a rollingresistance measurement is taken.

In the illustrated embodiment, the rolling means is a cylinder, and thearm extends at substantially 90° horizontally outward from the masscenter of the rolling means, and is further directed downward to alocation below the rolling means, whereby the swing weight is locatedsubstantially directly below the rolling means.

The swing weight may be round or may be made having flat surfaces.

The measuring means is selected from the group comprising sound andlight and the apparatus may further comprise means for collecting datafrom the measuring means, a computer for storing and analyzing the data,and means for outputting results.

Also provided is a method for measuring the rolling resistance of asubstrate comprising the steps of (a) providing an apparatus formeasuring the rolling resistance of a substrate, said apparatuscomprising a rolling means for rolling contact with a surface to bemeasured, an arm attached to the rolling means, the arm extendingdownward from the rolling means to free space below the rolling means, aswing weight integral with or attached to the arm distal from therolling means and in the free space, and measuring means located nearsaid free space for measuring the location of the swing weight relativeto the measuring means, and placing the apparatus on a substrate to bemeasured, (b) setting the swing weight in pendulum motion while therolling means rolls back and forth on the substrate, (c) measuring theamplitude of the motion of the swing weight for a period of timesufficient to determine the damping rate of the substrate, and (d)correlating the damping rate of the substrate with the rollingresistance of the substrate. The method may further comprise the step ofusing a lever attached to the rolling means for starting the motion ofthe swing weight and the rolling means by holding the lever down andreleasing the lever such that gravity initiates the motion and the levercontrols the initial amplitude of the motion by its length.

The swing weight may be selected to be a round swing weight or a swingweight with flat sides. When a round swing weight is selected, radar isthe preferred means of measuring the position of the swing weight, andwhen flat sides are on the swing weight, the means for measuring theposition of the swing weight may be means using sound or light.

The method may further comprise the steps of (a) creating a data base ofdamping rates for substrates tested, (b) setting up a ranking system tocorrelate a damping rate with rolling resistance for a specificsubstrate using alpha numeric labels representative of each ranking, and(c) comparing subsequent substrates tested for rolling resistance withthe ranking based on the damping rates observed for the subsequentsubstrates.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates an apparatus comprising a rolling means, a swingweight, and a measuring means.

FIG. 2 illustrates motion of the apparatus of FIG. 1 and means formeasuring the motion and collecting data.

FIG. 3 illustrates oscillation data for a first test substrate.

FIG. 4 illustrates oscillation data for a second test substrate.

FIG. 5 illustrates oscillation data for a third test substrate.

DETAILED DESCRIPTION OF THE INVENTION

With reference now to FIG. 1, a portion of the apparatus of theinvention 10 which contacts the material on which a rolling resistancemeasurement is being made, and the means of measuring the amplitude ofmovement of the apparatus is illustrated. The sample (substrate) 24 forwhich rolling resistance data is to be obtained, is placed on a flatsurface and the rolling means 12 of the apparatus is placed on thesubstrate 24 whereby an arm 14 connected to the rolling means 12 extendsdownward from rolling means 12 to a free space 36 below the substrate 24and the rolling means 12. In the illustrated embodiment, a swing weight16 is connected to arm 14 at a point distal from rolling means 12. Ameasuring device 20 is fixed in position in the proximity of swingweight 16.

Those skilled in the art will recognize that swing weight 16 is notneeded if arm 14 has a concentration of mass distal from rolling means12.

This portion of the apparatus 10 operates by sewing the swing weight (orthe distal end of arm 14) in motion, causing the rolling means 12 torock back and forth in contact with substrate 24.

The position of the swing weight 16 relative to roller 12 affects thedistribution of pressure exerted by roller 12 on a substrate 24. It isbelieved that the best results are obtained if the pressure distributionof roller 12 is substantially even on substrate 24. To this end, in themanufacture of apparatus 10, a Tekscan® sensor mat was used to measurethe pressure distribution of roller 12, and the information obtained wasused to adjust the position of swing weight 16 until an evendistribution was achieved. Those skilled in the art will recognize thatin embodiments of the apparatus where the position of swing weight 16 isnot adjustable, this technique can be used to develop a prototype havingeven pressure distribution, and subsequent apparatus can be made to thesame specifications as the prototype.

A lever 22 may be connected to rolling means 12 in order to standardizethe movement of the apparatus from sample to sample. For example, alever 22 of a specific length, when contacted with the flat surface orthe substrate 24, will always provide the same amplitude for the rockingmotion of rolling means 12 if arm 22 is pushed against the surface orsubstrate 24, for substrates having the same thickness, and released inthe same manner for each sample tested.

Those skilled in the art will recognize that other means may be used forstandardizing the motion of the rolling means 12 so that consistentinitial input is provided to the apparatus for each sample.

Rolling means 12 may be a cylinder, or a cube with a rounded bottom, orany other shape that provides a consistent rolling or rocking motion inthe apparatus.

Swing weight 16 may have any shape which is convenient for obtaining themeasurements provided by measuring device 20. For example, swing weight16 may be round if a radar measuring device is used, but a flat surface18 is desirable if ultrasonic, laser, or similar measuring devices areused.

It is preferred that the swing weight be substantially directly belowrolling means 12, in free space 36 that is sufficient to provideclearance for the motion of the swing weight when rolling means 12 rocksback and forth in the directions of arrow 32. In the illustratedembodiment, arm 14 extends from rolling means 12 at a 90° angle for adistance sufficient to clear the edge of the flat surface on which thesubstrate 24 is placed, then extends vertically downward at a 90° angle.An additional 90° angle in arm 14, substantially parallel to portion ofthe arm extending from rolling means 12, puts the distal end of arm 14substantially vertically below rolling means 12.

Those skilled in the art will recognize that arm 14 may be provided in asemicircle, or some portion of a circle, or for that matter a meanderingshape, which eventually brings the distal end of arm 14 substantiallyvertically below rolling means 12.

As discussed above, measuring device 20 may be any non-contact measuringdevice known in the art, and the swing weight 16 may be modified orshaped to accommodate whatever measuring device 20 is used.

With reference now to FIG. 2, the movement of arm 14 is illustrated inphantom lines when lever 22, also in phantom lines, is pressed againstsubstrate 24 on the flat surface on which rolling means 12 and substrate24 is placed. The length of lever 22 determines the distance, or thelength of path 31, which determines the maximum range of motion ofrolling means 12 on substrate 24.

Measuring device 20 is illustrated as bouncing sound waves or lightwaves 34 off flat surface 18, whereby the echo or reflection of thewaves is detected by measuring device 20 and used to measure thedistance between flat surface 18 and measuring device 20. The range ofmotion of swing weight 16, or amplitude, is a measure of how far rollingmeans 12 is rocking back and forth on substrate 24. If substrate 24 hasa high rolling resistance, this amplitude decreases rapidly, whereas ifsubstrate 24 has a low rolling resistance, this amplitude decreases moreslowly as air resistance, and the rolling resistance of the substrate,slowly brings the pendulum motion of the swing weight 16 to a stop. Therate of decrease of the pendulum motion is a measure of the rollingresistance of substate 24.

The motion measurements collected by measuring device 20 are transferredto a data logger 26 where the data is saved. The data may be downloadedfrom the data logger 26 during the test, or at some time after the testhas been run. A computer 28 may be used to calculate variances incondition to standardize the results, and to provide an output 30, forexample, a graph of the motion.

FIG. 3 illustrates the range of motion of swing weight 16, asinterpreted by measuring device 20, in dc voltage. As can be seen on thegraph, measuring device 20 has not been zeroed, but the voltage output,from lowest to highest, is an indication of the amplitude of the motion.The rate of decrease in amplitude is illustrated by the reduction of theamplitude over the period of time indicated horizontally on the graph.For example, in FIG. 3, the amplitude is substantially zero after about20 seconds. By comparison, the substrate tested in FIG. 4 shows that theamplitude of the swing weight has reached substantially zero at about 30seconds. By further comparison, the substrate tested as illustrated inFIG. 5 showed an amplitude of substantially zero after about 45 seconds.

The apparatus of the invention can be used to provide estimates ofenergy loss due to rolling friction in rubber sheets or blocks, or insubstrates comprising composites, for example cord reinforced belts. Thedevice can be used on a desk or a laboratory bench top.

What is claimed is:
 1. An apparatus for measuring the rolling resistanceof a substrate, said apparatus comprising (a) a rolling means forrolling contact with a surface to be measured; (b) an arm attached tosaid rolling means, said arm extending downward from said rolling meansto free space below said rolling means; (c) a swing weight integral withor attached to said arm distal from said rolling means and in said freespace, the rolling means, arm and swing weights forming a pendelum; and(d) measuring means located near said free space for measuring thelocation of said swing weight relative to said measuring means.
 2. Theapparatus of claim 1 further comprising a lever attached to said rollingmeans.
 3. The apparatus of claim 1 wherein said rolling means is acylinder.
 4. The apparatus of claim 1 wherein said arm extends atsubstantially 90° horizontally outward from the mass center of saidrolling means, and is further directed downward to a location verticallybelow said rolling means, whereby said swing weight is locatedsubstantially directly below said rolling means.
 5. The apparatus ofclaim 1 wherein said swing weight is round.
 6. The apparatus of claim 1wherein said swing weight has a flat surface.
 7. The apparatus of claim1 wherein said measuring means is selected from the group comprisingsound and light.
 8. The apparatus of claim 1 further comprising meansfor collecting data from said measuring means, a computer for storingand analyzing said data, and means for outputting results.
 9. A methodfor measuring the rolling resistance of a substrate comprising the stepsof (a) providing an apparatus for measuring the rolling resistance of asubstrate, said apparatus comprising a rolling means for rolling contactwith a surface to be measured, an arm attached to said rolling means,said arm extending downward from said rolling means to free space belowsaid rolling means, a swing weight integral with or attached to said armdistal from said rolling means and in said free space, and measuringmeans located near said free space for measuring the location of saidswing weight relative to said measuring means, and placing saidapparatus on a substrate to be measured; (b) setting said swing weightin pendulum motion while said rolling means rolls back and forth on saidsubstrate; (c) measuring the amplitude of the motion of said swingweight for a period of time sufficient to determine the damping rate ofsaid substrate; (d) correlating the damping rate of said substrate withthe rolling resistance of said substrate.
 10. The method of claim 9further comprising the step of using a lever attached to said rollingmeans for starting the motion of said swing weight and said rollingmeans by holding said lever down and releasing said lever such thatgravity initiates said motion and said lever controls the initialamplitude of said motion by its length.
 11. The method of claim 9 whichcomprises the further step of selecting a round swing weight for saidapparatus.
 12. The method of claim 11 comprising the further step ofselecting the means of measuring the position of a swing weight asradar.
 13. The method of claim 9 which comprises the further step ofselecting a swing weight having flat surfaces for said apparatus. 14.The method of claim 13 comprising the further step of selecting themeans for measuring the position of said swing weight from the groupcomprising sound and light.
 15. The method of claim 9 comprising thefurther steps of (a) creating a database of damping rates for compoundstested (b) setting up a ranking system to correlate a damping rate withrolling resistance for a specific substrate using alpha numeric labelsrepresentative of each ranking, and (c) comparing subsequent substratestested for rolling resistance with said ranking based on the dampingrates observed for said subsequent substrates.
 16. An apparatus formeasuring the rolling resistance of a substrate, said apparatuscomprising: (a) rolling means for rolling contact with a surface to bemeasured, an arm attached to the rolling means, the arm extendingdownward from the rolling means to free space below the rolling means, aswing weight integral with or attached to the arm distal from therolling means and in the free space; (b) means for setting the swingweight in pendulum motion while the rolling means rolls back and forthon the substrate; (c) means for measuring the amplitude of the motion ofthe swing weight for a period of time sufficient to determine thedamping rate of the substrate; (d) means correlating the damping rate ofthe substrate with the rolling resistance of the substrate.
 17. Anapparatus of claim 16, wherein the means of measuring the position ofthe swing weight comprises radar.
 18. An apparatus of claim 16, whereinthe means for measuring the position of the swing weight is selectedfrom a group comprising sound and light.
 19. An apparatus of claim 16,wherein further comprising: a lever attached to the rolling means forstarting the motion of the swing weight and the rolling means.
 20. Anapparatus of claim 16 further comprising: means for creating a databaseof damping rates for compounds tested; means for setting up a rankingsystem to correlate a damping rate with rolling resistance for aspecific substrate using alpha numeric labels representative of eachranking; and means for comparing subsequent substrates tested forrolling resistance with the ranking based on the damping rates observedfor the subsequent substrates.